One example of a water-proof connector is shown in JP-63-193471. This is provided with a male connector having a concave fitting member, and a female connector which fits into the concave member, the fitting portions of the two connectors being water-proofed by a ring-like seal member. Cylindrical rubber plugs are fitted on electric wires and are passed through terminal insertion holes in the rear face of each connector. The electric wires make contact with terminal fittings. These rubber plugs fit with the interior of the terminal insertion holes and thereby effect water-proofing.
Non-water-proof connectors, particularly female connectors into which square box-shaped female terminal fittings are inserted, have square terminal insertion holes openings in order to guide the square box-shapes, whereas the water-proof connectors described above have circular terminal insertion holes and rubber plugs in order to improve their seal.
Consequently, if one wants to effect water-proofing by fitting rubber plugs to each terminal insertion hole, the shape of the terminal insertion hole differs according to whether the connector is of a water-proof or non-water-proof type. As a result, the connectors cannot be interchanged. In particular, it is almost impossible to use a non-water-proof connector as a water-proof connector due to the sealing problems this would cause.
However, a water-proofing means which does not employ rubber plugs is described in JP-64-63282. This provides the rear face of the connector with a cover and has a layer of gel between the cover and the rear face of the connector, this gel covering a plurality of terminal insertion holes and thereby providing a seal. Accordingly, water-proofing is achieved irrespective of the shape of the openings of the terminal insertion holes.
Nonetheless, in this method of water-proofing, the cover seals only the terminal insertion holes on the rear face of the connector, and does not seal the fitting portion between this connector and the corresponding connector. As a result, a different sealing means is required.